Question

— You look scared. What happened?
— Well , I _______ along the street ________ the UFO landed.

A．was walking ; while	B．is walking ; when
C．was walking ; when	D．is walking ; while

Answer 1

C

此题重点考查when和while引导的时间状语从句的基本区别。When引导的时间状语从句常用一般时态，有时也用进行时态；while引导的时间状语从句常用进行时态。